1. Field of the Invention
The present invention relates to cheese base products, also known as cheese spreads and cheese dips, which contain vegetable matter. More particularly, the present invention provides a method for stabilizing a cheese base which contains vegetable matter, by buffering the vegetable matter prior its incorporation into the cheese base.
2. Description of the Background Art
Packaged, shelf-stable vegetables (such as canned and jarred vegetables) are acidified during the packaging process to increase their stability and shelf life. Unfortunately, the relatively low pH of such packaged vegetables renders them incompatible with heat-processed cheese based compositions (for example cheese dips) based on dairy protein emulsions. The high acidity of the vegetable matter causes the dairy emulsions to break down due to the acid-induced precipitation of one or more of the dairy proteins. The dairy proteins particularly problematic in this context include casein, lactalbumin and lactoglobulin. The isoelectric point of casein is about 4.6, while the isoelectric point of lactalbumin is 5.1 and of lactoglobulin is 5.3. Thus, the addition of vegetable matter having a pH of less than about 5.3 can cause dairy protein to precipitate out of heat-processed low solids cheese bases. This is unfortunate, as the high-acid canned vegetables represent a low-cost source of vegetable material. Because high acid content has previously rendered the low-cost canned vegetables unsuitable for use in the cheese-based products described herein, it has in the past been necessary to use higher-cost fresh vegetables for incorporation into the cheese based compositions.
The heat-processed cheese bases to which this invention is particularly directed contain a relatively low solids concentration (40% or less total solids) with no added gum stabilizers or binding agents such as carrageen or guar gum. These particularly preferred cheese bases are described in detail in U.S. patent application Ser. No. 08/038,075 which is a continuation of application Ser. No. 07/691,485 now abandoned, of even date herewith and incorporated by reference herein. The cheese bases are stable through a relatively prolonged retorting process, wherein relatively high heat is applied to sealed containers of the finished product. This stability to retort distinguishes these cheese bases from the pasteurized process cheese spreads (PPCS), which are not stable to the prolonged retorting process preferred for commercial packaging of glass jars. Vegetable matter, such as chopped tomatoes, jalapeno peppers and chile peppers are combined with the cheese base to produce cheese dips favored by consumers.
The process of this invention allows the pH of canned, drummed or jarred vegetables to be modified and stabilized (referred to as "equilibrated") so that the low solid, non-pasteurized cheese mixtures containing these particulates do not develop graininess, thermogelling or phase separation due to the acid induced deterioration of the emulsion.
U.S. Pat. No. 4,568,555 (Spanier; Feb. 4, 1986) describes a shelf stable cheese sauce which can contain dehydrated fruit and/or vegetable pieces, as opposed to the acid-packed vegetables employed in the present invention. There is no disclosure or suggestion of treating the vegetable matter with a buffer solution prior to the addition to the cheese base. The preparation of the cheese sauce involves preparing a starch/gum slurry, heated to 117.degree.-210.degree. F. To this slurry a mixture of cheese (5 to 15% by weight of cheese base), fats, water and flavorants are added. The vegetable pieces are then added to this cheese base. The sauce is filled into jars which are then capped and sterilized by retorting.
U.S. Pat. No. 4,840,806 (Hyldon et al.; Jun. 20, 1989) describes a tomato-based sauce which is stabilized by the addition of an acidic buffer followed by freezing to reduce the oxidative failure of the sauce. The buffer system used is designed to reduce and maintain the pH of the sauce to 4.2 or lower, and preferably between about 3.8 and 4.1, however.
There has remained a need in the art for a process that would allow the use of conventional, acidic, hot-packed vegetables such as canned tomatoes and peppers in the preparation of stable, retort-packaged cheese based products.